1. Field of the Invention
The present invention relates to a test system for use in testing an electronic device, such as a car audio system.
2. Related Background Art
In general, this type of electronic device is equipped with various units such as CD, cassette tape, MD, and DVD recorders in addition to a tuner. When manufacturing an electronic device including a plurality of units as stated above, it is necessary to execute a test to investigate whether various operations are performed normally in the units before shipment of the electronic device. The electronic device to be tested is hereinafter referred to as a target or a target device.
On testing the target including the plurality of units, it is necessary to test all operations that a user is likely to utilize. Therefore, with an increase of the number of units included in the target, required test items enormously increase. As a practical matter, there is even a case that it takes one month to complete the test.
It is explained here with a simple example. In testing a state where a target is turned off, a previous state of such a turned-off state should be put into a turned-on state in which power supply is given to the target. Similarly, a user may put a cassette tape recorder forming a unit from a playback state into a fast-rewind state or into a fast-forward state or a recording state. Furthermore, the user may stop listening to the cassette tape recorder and then switch the current mode to the CD, MD, DVD or any other mode. Therefore, consideration should be made about the possibility that, if the user switches the unit mode from the cassette tape to the CD, MD, DVD or any other mode, the user may select one of the playback, pause, stop, fast-forward, and fast-rewind functions for each unit to which the operation has been switched.
If the unit has a plurality of functions, it is necessary to test functions by the number of units before and after the switching and by the number of functions of each unit. Therefore, as the number of units included in the target and the number of functions of each unit increase more and more, the functions to be tested drastically increase.
Generally, a target including a plurality of units is tested by executing a program including a description of a test scenario corresponding to functions before and after the selection of each unit using a computer. In this case, each test scenario defines a predetermined state in a function of a unit before the selection as a start condition and a state after the execution as an end state, with a description of a test procedure varying with each test scenario.
Taking this into account, the target is automatically tested by using a computer. In this case, a control automatically progresses from a preceding test scenario to a following test scenario. If, however, the end state of the target according to the preceding test scenario differs from the start state of the target according to the following test scenario, it is necessary to follow a state transition procedure for causing a transition to occur in the target from the end state of the preceding test scenario to the start state of the following test scenario.
An increase of the number of units included in the electronic device and an increase of the functions thereof give rise to an increase of test scenarios and an increase of start states and end states. Particularly, an increase of states before and after a state transition requires a lot of state transition procedures more than the number of test scenarios. Therefore, it takes a time period of one month or so to test the target. Furthermore, if the number of states before and after the state transition changes due to a change in a target function or the like, a large number of state transition procedures should be prepared as well as test scenarios.
Hereinafter, the above test method will be described more specifically by referring to FIG. 9. The illustrated test scenario 1 describes a start state S1, a test procedure, and an end state S2. On the other hand, the test scenario 2 describes a start state S4, a test procedure, and an end state S3. Furthermore, the test scenario 3 describes a start state S2, a test procedure, and an end state S4.
It is assumed here that the test scenarios 1, 2, and 3 are executed in order. After the test scenario 1 is read into a test execution section and the test is executed according to the test procedure, the test scenario 1 is put in the end state S2. Therefore, in order to execute the test scenario 2 in the start state S4 subsequently, a transition procedure for a transition from the state S2 to the state S4 is executed in the test execution section after the execution of the test scenario 1 to cause a transition to the state S4 to occur. The transition to the state S4 brings about a start of the test procedure of the test scenario 2 in the test execution section and executes the test procedure to the end S3 thereof.
Subsequently, a transition procedure is started from the state S3 of the test scenario 2 to the start state S2 of the test scenario 3. Thus, the transition procedure from the end state S3 of the test scenario 2 to the start state S2 of the test scenario 3 is executed in the test execution section and the test of the test scenario 3 is executed according to the test procedure, thereby causing the end state S4.
As stated above, if the test scenarios are executed in series, it is necessary to cause a transition to the start state of the test scenario to be executed next. Therefore, the state transition often requires a different procedure even for the same transition destination if the transition starts from a different source. Accordingly, there is a need for defining a procedure individually according to a state of the transition source and a state of the transition destination. In this manner, as the number of states increases more and more, the number of states of the transition source and the transition destination increases, thereby increasing the number of definitions of the state transition procedure, too.
In addition, this type of target has functions increased by a change in installed devices (units) or by an increase of the devices. As a result, if the number of states for use in the test increases, it is necessary to define transition procedures to new states for all existing states. Furthermore, if the test scenarios are executed in series, it is necessary to prepare a state transition procedure adapted to the end state in which the previous test scenario has been executed and the start state of the next test scenario. Therefore, with a change in the execution order of the sequential execution procedure, the state transition procedure need be changed, too.
In any case, the practically used test method has a disadvantage that it cannot respond flexibly to an increase or a change in units included in a target to be tested.
On the other hand, the Japanese Unexamined Patent Publication No. 2002-189617 (Document D1) discloses an evaluation system and an evaluation method for evaluating a user system equipped with a microcomputer and with implementation of a user program and a real time operating system by using a host computer (a central processing unit). The invention in Document D1 has an advantage of eliminating a necessity for a use of a jig for the evaluation and a particular device such as an ICE.
The Japanese Unexamined Patent Publication No. Hei 10-63532 (patent document 2) discloses a test item generator for generating a test item for a controller whose motion is controlled by a microcomputer. The test item generator disclosed in the patent document 2 has event information transmitted from the controller to the microcomputer, a correspondence table between events and operations containing the event information and contents of operations of the controller so as to correspond to each other, a correspondence table between actions and motions containing action information transmitted from the microcomputer to the controller and contents of motions of the controller so as to correspond to each other, and a state transition table containing the event information and the action information so as to correspond to each other for each state transition.
In this structure, upon extracting event information and action information from the state transition table, a content of the operation and a content of the motion of the controller are converted on the basis of the correspondence table between events and operations and the correspondence table between actions and motions, and a result of the conversion is output as a test item.
According to the test item generator, a test item to be executed when the microcomputer is incorporated in the controller can be adjusted to actual specifications even if there is an inconsistency between the actual specifications of the controller and the design specifications of the program.
In the conventional technologies, however, there is no suggestion of problems caused to occur on an increase in the number of test scenarios with an increase in the number of units in a target, an increase in the number of the state transition procedures, or the like. For example, while Document D1 discloses the system and method for evaluating the user system to be a target, it neither refers to a test scenario in the host computer nor suggest any relation with a test scenario in a case of an increase or a decrease of the units in the target.
Furthermore, Document D2 only discloses an apparatus for generating a test item in a controller incorporating a microcomputer. No disclosure is made about testing the target externally. In addition, Document D2 does not describe any problem that results from an increase in the state transition information.